At present, fluorine-containing carboxylic acids are used for a wide variety of utilities such as surface active agents or surface treating agents because of their excellent stability, chemical resistance, weather resistance, water- and oil-repellency, and are also useful as intermediates for the synthesis of physiologically active substances. The fluorine-containing carboxylic acid esters obtained by the process of this invention are important intermediates for the synthesis of various useful compounds having the above-described properties.
Typical conventional processes for preparing fluorine-containing carboxylic acid ester derivatives comprise the Reppe method using a fluorine-containing substituted ethylene. Examples of the conventional processes include (1) a process comprising reacting a perfluorooctylethylene with carbon monoxide at 380 atms. in ethanol in the presence of a palladium catalyst and an alcoholic hydrogen chloride at a temperature of 140.degree. C. for 7 hours to obtain a mixture of ethyl .alpha.- and .beta.-perfluorooctylpropionate, as described in German OLS No. 2137712; (2) a process comprising reacting trifluoropropene with an alcohol in the presence of a divalent palladium catalyst having a tertiary phosphine ligand under a carbon monoxide pressure of 110 atms. at a temperature of from 100.degree. to 125.degree. C. for a period of from 30 to 70 hours to obtain a mixture of ethyl .alpha.- and .beta.-trifluoromethylpropionate, as described in T. Fuchikami, K. Ohishi and I. Ojima, J. Org. Chem., Vol. 48, 3803 (1983), etc. However, each of the above conventional processes (1) and (2) is not advantageous in that the selectivity to the position of carbon atom where carbonylation occurs is low. That is, although ethyl .beta.-perfluoroalkyl propionate is produced preferentially, an .alpha.-substituted product is also produced in a substantial amount, and these products are difficult to separate into respective pure product. Further, the above conventional processes require a carbon monoxide pressure higher than 100 atms. and, hence, are very expensive in order to secure safety of the process.
As a result of extensive studies for overcoming the disadvantages of the conventional processes, the present inventors found that a single carbonylated product, i.e., a fluorine-containing carboxylic acid ester represented by the formula (I) can be produced in high yield according to the process of this invention.